Core A is responsible for cohort follow-up and database maintenance in the Nurses'Health Study. The specific aims for this core are as follows: 1) Develop and mail biennial follow-up questionnaires to cohort participants 2) Process returned questionnaires and verify responses 3) Compile databases of exposure data 4) Trace lost participants and maintain an updated name and address file 5) Sustain high cohort participation Under the direction of Diane Feskanich, ScD, Core A develops and designs the questionnaire for biennial follow-up of study participants. Questionnaire design incorporates input from all investigators on the Program Project, as well as other collaborating investigators, through bi-weekly meetings. New questions are pilot tested and follow-up methods are refined to address the needs of the cohort members. Returned questionnaires are checked for completeness, optically scanned, and verified for errors. Over 80,000 questionnaires are returned in every follow-up cycle. Core A uses a range of methods to trace participants and to maintain a high 90% response rate. Returned questionnaires are digitally imaged and stored on DVD, from which they are easily retrievable. Exposure data from the questionnaires are complied into databases and variables are derived and documented for use by investigators. This includes maintenance of nutrient intakes derived from the food frequency portion of the questionnaire. Diseases reported on the questionnaires are passed to Core B for confirmation.